In conventional angular velocity sensors disclosed, for example, in Japanese Patent Non-examined Publication No. H10-332378, a vibrator is directly supported by terminals. The conventional angular velocity sensor will be described below with reference to the accompanying drawings. FIG. 21 is a perspective view of the conventional angular velocity sensor and FIG. 22 is a circuit diagram of the angular velocity sensor.
In FIG. 21 and FIG. 22, vibrator 1 in a rectangular parallelepiped shape is constructed by laminating first piezoelectric substrate 2 to second piezoelectric substrate 4 via electrode layer 3. On the top side of vibrator I, there are provided two split electrodes 5 serving for both driving and detecting roles, while on the underside, there is provided common electrode 6. Four terminals 7 substantially in a Z-shape are each held in place by having widened portion 8 at one end thereof soldered to split electrode 5 of vibrator 1 at a nodal point of vibration of vibrator 1. The other end is projected to the outside. Such an angular velocity sensor has a circuit configuration as shown in FIG. 22. More specifically, split electrodes 5 are each connected with one output terminal of oscillator circuit 9 as the driving source via respective resistors 10, while common electrode 6 is connected with the other output terminal of oscillator circuit 9. Further, split electrodes 5 are each connected to noninverting input (+) and inverting input (−) of differential amplifier 12 via respective resistors 11. Further, the output terminal of differential amplifier 12 and inverting input (−) of differential amplifier 12 are connected by resistor 13.
Operation will be described of the conventional angular velocity sensor configured as above.
Oscillator circuit 9 outputs a driving signal such as a sinusoidal wave signal and applies it to split electrodes 5 of vibrator 1 via resistors 10. Then, first piezoelectric substrate 2 and second piezoelectric substrate 4 generate bending vibrations perpendicularly to their principal planes. If vibrator 1 rotates round its center axis, a Coriolis force corresponding to the rotational angular velocity is generated. The Coriolis force generated at this time acts in a direction parallel to the principal planes of first piezoelectric substrate 2 and second piezoelectric substrate 4 and perpendicular to the center axis of vibrator 1. By this Coriolis force, the direction of the bending vibration of vibrator 1 is changed and, hence, split electrodes 5 generate a signal corresponding to the angular velocity. Then, differential amplifier 12 detects the signal generated in split electrodes 5 via resistors 11 and, thus, the angular velocity applied to the angular velocity sensor is detected.
In the described configuration, terminals 7 are held in place by being soldered to split electrodes 5 of vibrator 1 at nodal points of vibration of vibrator 1. Accordingly, if the area of each node of vibration is reduced in order to obtain a smaller-sized vibrator 1, it also becomes necessary to make corresponding terminals 7 and widened portions 8 smaller. Consequently, the strength for holding vibrator 1 is lowered. Therefore, when the angular velocity sensor is subjected to strong vibrations, the connections between vibrator 1 and terminals 7 becomes unstable and the output characteristic of the angular velocity sensor is deteriorated.